In long-lasting deformation of keratin fibers such as hair, first the disulphide bonds —S—S— of the keratin (cystine) are opened using a composition containing a suitable reducing agent (reduction stage), then the hair thus treated is optionally rinsed, secondly the disulphide bonds are reconstituted by applying, on the keratin fibers previously put under tension (curlers etc.), an oxidizing composition (oxidation stage, also called fixation) so as to finally give the keratin fibers the desired form. This technique thus makes it possible to carry out either waving or straightening of the keratin fibers. For example, JP-B-S62-9566 or U.S. Pat. No. 4,459,284 discloses a standard process for permanent waving or straightening of keratin fibers such as hair in line with the above steps.
The new shape imposed on the keratin fibers by chemical treatment as described above is relatively long-lasting and notably withstands the action of washing with water or shampoo, in contrast to the simple conventional techniques of temporary styling by using foams, styling gels, or lacquers.
Many compositions and processes for the above chemical treatment have been proposed. Generally, they offer good performance on the day of treatment.
However, there are various drawbacks such as follows in the above chemical treatment process that may not be suitable from the view-point of consumer's or hair-dresser's expectations:                Insufficient reshaping efficiency such as weak wave intensity;        Poor usability caused by, for example, dripping of the composition from the hair;        High levels of keratin fiber degradation, especially in repeated applications or in combination with other chemical treatments such as oxidative coloration;        Long processing time; and        Malodor of ammonia or sulfur-containing compounds during and after the deformation process.        
In particular, sufficient reshaping efficiency, short processing time, and conditioning effects to keratin fibers are important. There is indeed a need to improve a deformation process of keratin fibers to provide sufficient reshaping efficiency, such as strong wave intensity of the curled keratin fibers, as well as excellent hair conditioning effects such as conditioning feel, in a relatively short period of time. In addition, excellent usability such as no or reduced malodor is also desirable.